Acid nickel electroplating

ABSTRACT

PRIMARY BRIGHTENERS FOR ACID NICKEL ELECTROPLATING BATHS AND PROCESS ARE PROVIDED. THE PRIMARY BRIGHTENER ADDITIVES ARE ACRYLATES SELECTED FROM THE GROUP CONSISTING OF (1) AN ACRYLATE MONOMER OF THE FORMULA:   CH2=C(-R)-COO-CNH2N-N+(-R&#39;&#39;)2-R&#34; X(-)   WHEREIN R IS METHYL OR HYDROGEN, N IS A POSITIVE WHOLE INTEGER OF 1 TO 3 INCLUSIVE, R&#39;&#39; IS ALKYL OF 1 TO 4 CARBON ATOMS, R&#34; IS ALKYL OF 1 TO 4 CARBON ATOMS,   -CH2CH=CH2   -CH2C$CH, -CH2COOCH3,   -CH2COOC2H3,   -CH2COR WHERE R IS AS DEFINED ABOVE, -CH2CONH2, -CH3CN, -CH2CH2OH, -CH2CH2COO- OR -CH2CH3CH2SO3- AND X- IS CH3SO4-, C2H5SO4, HALIDE OR IS ABSENT WHEN R&#34; IS -CH2CH2COO- OR   -CH2CH2CH2SO3-   (2) A HOMOPOLYMER OF SAID ACRYLATE MONOMER, AND (3) A COPOLYMER OF SAID ACRYLATE MONOMER WITH AT LEAST ONE ETHYLENICALLY UNSATURATED MONOMER SELECTED FROM THE GROUP CONSISTING OF AN A,B-ETHYLENICALLY UNSATURATED MONOCARBOXYLIC ACID, AN ALKYL ESTER OF SAID ACID WHEREIN THE ALKYL GROUP IS FROM 1 TO 4 CARBON ATOMS, ACRYLONITRILE, ACRYLAMIDE, METHACRYLAMIDE, VINYL ACETATE, VINYL SULFONE AND VINYL PYRIDINE, THE MOLAR RATIO OF SAID ACRYLATE MONOMER OF SAID UNSATURATED MONOMER BEING WITHIN THE RANGE OF 0.9:0.1 TO 0.1:0.9.

"United States Patent 3,723,260 ACID NICKEL ELECTROPLATING John Derek Rushmere, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del. No Drawing. Filed Feb. 15, 1972, Ser. No. 226,543 Int. Cl. C23b /08, 5/46 US. Cl. 20449 20 Claims ABSTRACT OF THE DISCLOSURE Primary brighteners for acid nickel electroplating baths and processes are provided. The primary brightener additives are acrylates selected from the group consisting of (1) an acrylate monomer of the formula:

wherein R is methyl or hydrogen,

n is a positive whole integer of 1 to 3 inclusive, R is alkyl of 1 to 4 carbon atoms,

-R" is alkyl of 1 to 4 carbon atoms,

(2) a homopolymer of said acrylate monomer, and

(3) a copolymer of said acrylate monomer With at least one ethylenically unsaturated monomer selected from the group consisting of an a,,9-ethylenically unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from 1 to 4 carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the molar ratio of said acrylate monomer to said unsaturated monomer being within the range of 0.9:(11 to 0.1 :0.9.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to acid nickel electroplating baths and processes.

Prior art 3,723,260 Patented Mar. 27, 1973 are generally divided into two classes on the basis of their predominant function. Primary brighteners are materials used in relatively low concentration which by themselves may or may not produce visible brightening action. However, some primary brighteners, when used alone, also produce some deletrious side eifects such as deposit brittleness, narrow bright plate range and skip plating at low current densities. Secondary brighteners are materials which are usually used in combination with primary brighteners, but at a higher concentration. Secondary brighteners, by themselves, may produce some brightening action, but the deposits are usually not mirror bright and the rate of brightening is usually inadequate.

When primary and secondary brighteners are carefully selected, it is possible to obtain over a wide current density range ductile and leveled deposits at a good brightening rate.

In the patent art, US. Pat. 2,647,866 (issued to Henry Brown on Aug. 4, 1953) discloses the use of various pyridinium compounds, e.g., N-allyl pyridinium bromide as primary additives for bright nickel plating. This patent also teaches the use of the pyridinium compounds in conjunction with organic sulfonic, sulfonamide and sulfonirnide compounds which are the subjects of US. Pats. 2,191,813 and 2,466,677 also issued to Henry Brown. The use of various acetylenic compounds, e.g., 2-butyne-1,4- diol, as primary brighteners again used in conjunction with aromatic sulfur compounds is the subject of U.S.. Pat. 2,712,522 issued to Otto Kardos et al. on July 5, 1955. More recently, US. Pat. 3,296,103 (issued to Frank Passal on Jan. 3, 1967) teaches the use of compounds combining both pyridinium and acetylenic functions, e.g., 1-

. propargyl, S-carboxamido pyridinium bromide as primary brighteners, again in conjunction with various sulfur compounds. Esters of unsaturated monocarboxylic acids, e.g., methyl acrylate used as primary brighteners is the subject of US. Pat. 2,690,996 (issued to Henry Brown on Oct. 5, 1954)..

SUMMARY OF THE INVENTION According to the present invention, there is provided an aqueous acid nickel electroplating bath comprising an aqueous solution of a nickel salt, said solution maintained at a pH in the range of about 3 to 5 and having dissolved therein as primary brightener in an elfective amount, an acrylate selected from the group consisting of (1) an acrylate monomer of the formula:

R is methyl or hydrogen,

n is a positive whole integer of 1 to 3 inclusive,

R' is alkyl of 1 to 4 carbon atoms,

R is alkyl of 1 to 4 carbon atoms, CH CH=CH CH2'CECH, CH COOCH -CH COOC H -CH C'OR where R is as defined above,

(2) a homopolymer of said acrylate monomers, and

(3) a copolymer of said acrylate monomer with at least one ethylenically unsaturated monomer selected from the group consisting of an :,13-CthYiCl1iC3liY unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from 1 to 4 carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the molar ratio of said acrylate monomer to said unsaturated monomer being within the range of 09:01 to 01:09.

There is also provided a process of electroplating bright nickel from the aforesaid electroplating bath.

DETAILED DESCRIPTION OF THE INVENTION Generally, the invention pertains to the electro-deposition of nickel from aqueous, acidic nickel electroplating baths known to those skilled in the art. These baths are usually formed by the dissolution of at least one nickel salt in an aqueous, acid solution. Conventional baths and processes for electroplating bright nickel are described in Principles of Electroplating and Electroforming, Blum and Hogaboom, pages 362-381, revised third edition, 1949, McGraw-Hill, Inc., New York; and in Modern Electroplating, edited by A. G. Gray, The Electrochemical Society, 1953, pages 299-355. Operating conditions disclosed, including pH, temperature, current density and the concentration of bath ingredients are applicable to the present invention. Generally, the pH will be in the range of 3 to and usually 3.5 to 4.5, while the temperature will be in the range of 40 to 70 C. and usually 55 to 65 C. Practically all baths for electroplating bright nickel contain nickel sulfate; a chloride, usually nickel chloride; a buffering agent, usually boric acid; and optionally a wetting agent. Such baths include the well-known Watts bath and the high chloride bath. Other baths may contain, as the source of nickel, a combination of nickel fluoborate with nickel sulfate and nickel chloride, or a combination of nickel fluoborate with nickel chloride. Typical Watts baths and high chloride baths are as follows:

Watts baths Nickel sulfate g./l 200-400 Nickel chloride g./l 30-75 Boric acid g./l 30-50 Temperature C 55-65 pH 3-5 High chloride baths Nickel chloride g./l 150-300 Nickel sulfate g./l 40-150 Boric acid g./l 30-50 Temperature C 55-65 pH 3-5 The primary brighteners of the present invention may be used in concentrations ranging between about 0.001 to 5 g./l., preferably between about 0.002 to 2 g./l., the particular concentration used depending on the types and concentrations of secondary and secondary auxiliary brighteners used. Other factors to be considered are concentrations of the bath ingredients, bath operating conditions and the degree and rate of brightening and leveling desired.

The primary brighteners of this invention are certain quaternized dialkylaminoalkylacrylate monomers and more particularly homopolymers of these monomers or copolymers of these monomers with other ethylenically unsaturated monomers. The quaternized dialkylaminoalkylacrylates used in this invention have the general formula:

wherein R is methyl or hydrogen,

n is a positive whole integer of l to 3 inclusive,

R is alkyl of 1 to 4 carbon atoms,

R" is alkyl of 1 to 4 carbon atoms, -CH CH=CH --CH COR Where R is as defined above,

-CH CONH (2) a homopolymer of said acrylate monomer, and

(3) a copolymer of said acrylate monomer with at least one ethylenically unsaturated monomer selected from the group consisting of an age-ethylenically unsaturated monocarboxylic acid, and alkyl ester of said acid wherein the alkyl group is from 1 to 4 carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the molar ratio of said acrylate monomer to said unsaturated monomer being within the range of 0.9:0.1 to 0.1209.

One monomer falling under this general description which has been found to be particularly useful as a primary brightener is: Z-methacryloxyethyl, dimethyl propargyl ammonium bromide which may be prepared by the addition of propargyl bromide to dimethylaminoethyl methacrylate in a suitable solvent.

This monomer may be readily polymerized in aqueous solution under the action of a peroxide initiator and a temperature of 60 to C. to give a homopolymer which shows enhanced brightening-leveling characteristics over the monomer but which also inhibits plating at low current densities, i.e., less than 10 amps/ft The problem of low current density skipping, while retaining brightening-leveling characteristics, is overcome by copolymerizing the quaternized dialkylaminoalkylacrylates with at least one other ethylenically unsaturated monomer such as an a,fi-ethylenically unsaturated monocarboxylic acid such as acrylic acid or methacrylic acid, an alkyl ester of said acid wherein the alkyl group is from 1 to 4 carbon atoms, methacrylamide, acrylamide, acrylonitrile, vinyl acetate, vinyl sulfone, and vinyl pyridine. The molar ratios of the acrylate monomer to the other monomer can vary between about 0.9/0.1 to 0.1/0.9. Of particular interest-in this capacity is the copolymer formed between: Z-methacryloxyethyl trimethyl ammonium methyl sulfate and methacrylic acid CH: CHa

The above copolymer is preferably used with molar ratios of n/m varying between 0.7/0.3 to 0.3/0.7, although maximum benefits are obtained at ratios of n/m about 0.7/O.3.

Many primary brightener equivalents will be readily apparent to one skilled in the art. Thus, some benefits would be expected for the copolymers of the quaternized dialkylaminoalkyl acrylates with any other copolymerizable ethylenically unsaturated monomer. Further, the invention includes terpolymers, tetrapolymers and other copolymers.

Secondary brighteners, usually used at a concentration of 1 to 20 g./l., may consist typically of aromatic sulfonates, sulfonamides or sulfimides such as sodium or potassium salts of saccharin, 1,3,6-naphthalene trisulfonate p-toluene sulfonamide, benzene sulfonic acid (usually in form of sodium or potassium salt). The secondary brighteners are generally characterized by having at least one sulfone or sulfonic acid group attached to a nuclear carbon of a homocyclic aromatic ring. These maproximately a mole for mole basis the quaternizing agent to the dimethylaminoethylmethacrylate in a suitable solvent, and found to have a brightening-leveling ability.

TABLE I.-Q,UATE RNIZED DIMETHYLAMINOEIHYLME THAG RYLATES Norm-C=2-methacryloxyethyl, carbomethoxymethyl, dimethyl ammonium chloride; D =2-methaeryloxethyl, eyanomethyl, dimethyl ammonium chloride: E=2-mcthaeryloxyethyl, dimethyl, 3-suliopropyl ammonium betaine.

terials have a brightening elfect on the nickel deposits but, more importantly, impart ductility.

In addition, other sulfonated unsaturated hydrocarbons, such as sodium allyl sulfonate and sodium-3-chloro-2-butene-l-sulfonate may be added to the bath as auxiliary secondary brighteners to further improve the brightness range and ductility of the nickel deposits. Auxiliary secondary brighteners as well as the secondary brighteners are well-known to those skilled in the art.

The invention can be further understood by referring to the following examples in which parts and percentages are by weight unlessotherwise indicated. In each of the examples, an aqueous, acid nickel bath of the following composition was used as the base solution:

G./l. Nickel sulfate 300 Nichel chloride 60 Boric acid 45 Saccharin 2 Sodium alkyl sulfonate 2 pH 4 Additives were added to this base bath in 267 ml. Hull Cell tests. The tests were conducted at 60-65 C. using steel panels, and electroplating was at 2 amps. for minutes. Agitation of the bath was accomplished by a mechanical stirrer sweeping parallel to the panels. Prior to plating, each panel was anodically cleaned, scratched lengthwise with one pass of 240 grit emory cloth to enable a visual comparison of leveling to be made, and again anodically cleaned.

EXAMPLE 1 EXAMPLE 2 Z-methacryloxyethyl, carboxamidomethyl, dimethyl ammonium chloride (B) was prepared by standing together 9.4 g. of chloroacetamide and 8 g. dimethylaminoethylmethacrylate in g. dimethyl formamide for 12 days. After this time, a few white solids had appeared. On pouring the solution into methyl ethyl ketone, considerable white crystalline solids precipitated. They contained Cl: 13.92%. Theory for C1: 14.18%.

In a Hull Cell test using (B) in an amount of 0.16 g./l. of plating bath, the panel showed very bright nickel above about 12 a./ft. The degree of leveling was good, i.e., most of the scratch lines were covered.

EXAMPLES 3-5 In Table I are listed other quaternized dimethylaminoethylmethacrylates which were prepared by adding on ap- EXAMPLE 6 Z-methacryloxethyl, dimethyl, allyl ammonium bromide (F) was prepared by adding 12 g. allyl bromide to 8 g. dimethylaminoethylmethacrylate in 25 g. methyl ethyl ketone. The white crystals were found to contain 29.0% Br. Theory 28.8%. Used in amounts of 0.02-0.16 g./l. of plating bath. (F) was found to have only marginal action as a brightener-leveler. Consequently, (F) was polymerized by warming together 5 g. (F), 25 g. water, 0.05 g. potassium persulfate in a stirred vessel at C. for 1 hour. Poly (F) was precipitated as a white rubbery material on pouring into acetone. After drying at 60 C. under vacuum, brownish brittle solids, easily soluble in water, were obtained.

In a Hull Cell plating test, using poly (F) in an amount of 0.04 g./l. of plating bath, poly (F) was found to be an excellent brightener-leveler above 40 a./ft. The nickel deposit was mirror bright with all scratches completely leveled. Lesser amounts of poly (F) in the plating bath permitted nickel deposition below 40 a./ft. but with some loss of leveling ability. Thus, at 0.008 g./l., bright nickel was obtained above 1 a./ft. but only slight leveling was observed.

EXAMPLES 7-12 In Table II are listed other homopolymers prepared in a manner similar to that of Example 6 and found to have brightening-leveling action when added to the nickel bath in amounts of 0.008 g./l. to 0.04 g./l.

EXAMPLES 13-18 A series of copolymers of Z-methacryloxyethyl trimethyl ammonium methyl sulfate (M) with methacrylic acid (N) in mol. ratios of M/N varying between 0.9/0.1 and 0.1/0.9 were prepared by polymerizing the monomers together in aqueous solution, using potassium persulfate as catalyst. Reaction conditions were total monomers 0.1 mole; concentration in aqueous solution, 20-30% by weight; potassium persulfate, 0.02 to 0.09 g.; temperature, 80 C.; time, 20-60 minutes. The polymers were precipitated in acetone and dried under vacuum at 60 C. to give brittle, colorless Solids easily soluble in water. Composition was found by microanalysis and is shown in Table III together with plating performance.

TABLE III.2-METHACRYLOXYETHYL TRIMETHYL AMMONIUM METHYLSULFATE (M)-METHACRYLIC ACID (N) COPOLYMERS Mols Found, percent Bright Example Amount range, Levelnumbcr M N C H N S I.V. g /l AJft. ling 0. 14 42. 36 7. 77 4. 72 1O 55 0. 02 2 G-E NOTE.I.V.=Intrinsic Viscosity (by flow viscosimeter); levelling, S=slight, few scratches covered; F=iair; G=go0d, most scratches covered; E=exccllcnt, virtually all scratches covered.

EXAMPLES 1923 2. The acid electroplating bath of claim 1 wherein the acrylate is a copolymer of an acrylate monomer of the general formula:

wherein R is methyl or hydrogen, R' is methyl or ethyl,

TABLE IV.Q,UATERNIZED DIALKYLAMINOETHYLAORYLATE (X)VINYL (Y) COPOLYMERS M01 Bright ratio, Amount, range, Level- Extnnplc X Y X/Y g./l. u/it. ling 19 Q-methacryloxycthyl trimethyl ammo- Methyl mcth- 0. 5/05 0.02 4 FG nium methyl sulfate. acrylate.

20 do Methaerylamide... 0.5/0.5 0.04 40 E Acrylonitrile 0.5/0.5 0. 04 24 G 22 d0 Acrylic acid 0.7/0.3 0.04 20 G 23 2-acryloxycthyl trimethyl ammonium do 0.5/0.5 0.04 4 F methyl sulfate.

What is claimed is:

1. An aqueous acid nickel electroplating bath comprising an aqueous solution of a nickel salt, said solution maintained at a pH in the range of about 3 to 5 and having dissolved therein as primary brightener an effective amount of an acrylate selected from the group consisting of (1) an acrylate monomer of the formula:

wherein R is methyl or hydrogen,

n is a positive whole integer of 1 to 3 inclusive, R is alkyl of 1 to 4 carbon atoms,

R" is alkyl of 1 to 4 carbon atoms,

where R is as defined above, -CH CONH CH CN, --CH CH OH, CH CH COO or -CH2CH2'CHZSO3 and X is CH2SO4, C2H5SO4 Or is absent when R is CH CH COO- or CH CH CH SO (2) a homopolymer of said acrylate monomer, and (3) a copolymer of said acrylate monomer with at least one ethylenically unsaturated monomer selected from the group consisting of an a, fl-e'thylenically unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from 1 to 4 carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the molar ratio of said acrylate monomer to said unsaturated monomer being within the range of 0.9101 to 0.1209.

R" is alkyl of 1 to 4 carbon atoms, CH CH=CH -CH2CECH, CH COOCH CH COOC H -CH COR where R is as defined above,

CH CONH CH CN, -CH CH O-H with at least one ethylenically unsaturated monomer selected from the group consisting of an a, B-ethylenically unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from 1 to 4 carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the copolymer having a molar ratio of said acrylate monomer to said unsaturated monomer being within the range of 0.7/0.3 to 0.3/0.7.

3. The acid electroplating bath of claim 2 wherein the pH of the bath is within the range of about 3.5 to 4.5 and the copolymer concentration is about 0.001 to 5 g./l.

4. The acid electroplating bath of claim 3 wherein the copolymer concentration is about 0.002 to 2 g./1.

5. The acid electroplating bath of claim 2 wherein the ethylenically unsaturated monomer is methacrylic acid.

6. The acid electroplating bath of claim 2 wherein the copolymer is about 70 molar percent of Z-rnethacryloxyethyl, trimethyl ammonium methyl sulfate and about 30 molar percent of methacrylic acid.

7. The acid electroplating bath of claim 1 wherein the acrylate is an acrylate monomer of the general formula:

wherein R is methyl or hydrogen, R is methyl or ethyl, R" is alkyl of 1 to 4 carbon atoms,

-CH COOC H -CH COR where R is as defined above,

CH CONH CH CN, CH CH OH 8. The acid electroplating bath of claim 7 wherein the acrylate monomer is 2-methacryloxymethyl, dimethyl propargyl ammonium bromide or Z-acryloxyethyl, diethyl propargyl ammonium bromide.

9. The acid electroplating bath of claim 7 wherein the pH of the bath is within the range of about 3.5 to 4.5 and the acrylate monomer concentration is about 0.001 to 5 g./l.

10. The acid electroplating bath of claim 1 wherein the acrylate is a homopolymer of an acrylate monomer of the general formula:

wherein.

R is methyl or hydrogen, R is methyl or ethyl, R is alkyl of 1 to 4 carbon atoms, -CH 'CH-=CH CHZCEOH, CH CO'0CH C CO'C H CH COR where R is as defined above,

--CH 'CONH -CH CN, -CH CH OH CH SO C H SO halide or is absent when R" is 11. The acid electroplating bath of claim wherein the pH of the bath is within the range of about 3.5 to 4.5 and the acrylate homopolymer concentration is about 0.001 to 5 g./l.

12. The acid electroplating bath of claim 1 wherein the acrylate is added to give a bath concentration within the range of about 0.001 to 5 g./l.

13. In a process of electroplating nickel from an aqueous acid nickel electroplating bath having a nickel salt dissolved therein the improvement comprising: maintaining said bath at a pH in the range of about 3 to 5 and adding thereto as a primary brightener an elfective amount of an acrylate selected from the group consisting of:

(1) an acrylate monomer of the formula:

CHz=C-EO--C,,HznN+(R)zR"X- I?. wherein R is methyl or hydrogen, n is a positive whole integer of 1 to 3 inclusive, R is alkyl of 1 to 4 carbon atoms, R" is alkyl of 1 to 4 carbon atoms,

-CH CH='CH OH CiEOH -CH C0OCH -CH COOC H CH COR where R is as defined above, CH CONH -CH CN, -CH CH OH, -CH CH COO* or CH CH CH SO and X- is CH SO C H SO halide or is absent when R" is -CH OH COO- or -OH CH CH SO (2) a homopolymer of said acrylate monomer and (3) a copolymer of said acrylate monomer with at least one ethylenically unsaturated monomer selected from the group consisting of an a, ,B-ethylenically unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from 1 to 4 10 carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the molar ratio of said acrylate monomer to said unsaturated monomer being within the range of 09:01 to 0.1209.

14. The process of claim 20 wherein the acrylate is added to give a bath concentration of about 0.002 to 2 g./l., the pH is maintained within the range of about 3.5 to 4.5 and the bath is at a temperature in the range of about 40 to 70 C.

15. The process of claim 14 wherein the acrylate is a copolymer of an acrylate monomer of the general formula:

wherein R is methyl or hydrogen, R is methyl or ethyl, R" is alkyl of 1 to 4 carbon atoms, CH CI-I=CH -CH COR where R is as defined above,

CH CONH -CH OH, --CH CH OH,

CH CH COO- or CH CH CH SO and X is CH SO C H SO halide or is absent when R" is 01' CH2CH2CH2SO3 with at least one ethylenically unsaturated monomer selected from the group consisting of an ac, B-ethylenically unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from 1 to 4 carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the copolymer having a molar ratio of said acrylate monomer to said unsaturated monomer within the range of 0.7/0.3 to 0.3/0.7 and the bath is at a temperature in the range of about 20 to 30 C.

16. The process of claim 15 wherein the ethylenically unsaturated monomer is methacrylic acid.

17. The process of claim 15 wherein the copolymer is about 70 molar percent of 2-methacryloxyethyl, trimethyl ammonium methyl sulfate and about 30 molar percent of methacrylic acid.

18. The process of claim 14 wherein the acrylate is an acrylate monomer of the formula:

wherein R is methyl or hydrogen, R is methyl or ethyl,

R" is alkyl of 1 to 4 carbon atoms, CH CH=CH CHzOOJCHg, CHzCO OCgH CH COR Where R is as defined above, C'H OONH -CH CN, CH OH OH, -CH CH COO" or -CH2CH2CH2SO'3 and X- is CH SO C H SO4-, halide or is absent when R" is OI CH CH CH SO 19. The process of claim 14 wherein the acrylate is a homopolymer of an acrylate monomer of the general formula:

11 wherein 20. The process of claim 13 wherein the acrylate is dded to give a bath concentration within the range of R is methyl or hydrogen, a R! is methyl or y about to 5 R is alkyl of 1 to 4 carbon atoms, CH CH=CH 5 References Cited CH COR where R is as defined above, 2,893,933 7/1969 Winters et a1. 20449 CH2CONH2, cH,cN, CHZOHZOH, 3,574,067 4/ 1971 Spiro 204 49x 10 CH H 00 or ,CH2CH2CH2SO3 and is GERALD L. KAPLAN, Primary Examlner CH3SO4 C H SO halide 01' is absent when R is U S cl X R 

